1. Field of the Invention
The present invention relates to gas discharge display devices having a gas filled sealed chamber which is divided by a control disc into a gas discharge chamber and a post-acceleration chamber, and in particular to such a gas discharge display device having a spacing frame for the post-acceleration chamber which allows use of high post-acceleration voltages without arcing.
2. Description of the Prior Art
Gas discharge display devices are known in the art which consist of a gas filled chamber which is terminated in gas-tight fashion on one side by a front plate and on the opposite side by a rear plate and which is subdivided by a control disc parallel to the front and back plates into a gas discharge chamber on the cathode side and a post-acceleration chamber on the anode side are known in the art. The control disc for such devices has electrode paths which are separately driveable which are disposed on one side of the disc as parallel row conductors and on the opposite side as column conductors, which together form a matrix with the disc being perforated at the intersection points of the rows and columns for permitting controlled plasma flow therethrough. The interior of the front plate has a luminescent screen provided with an anode layer and the interior of the rear plate has one or more cathodes which are insulated with respect to each other. A spacing frame is provided between the control disc and the luminescent screen, as well as between the control disc and the cathode(s).
A gas discharge display device of the type described above having a cathode consisting of parallel cathode strips which are insulated from one another and are separately driveable is disclosed in German OS No. 26 43 915, corresponding to U.S. Pat. No. 4,130,778. The division of the cathode into separated cathode strips which are insulated from one another is an improvement over a similar device employing a plate cathode which is known from German OS No. 24 12 869 corresponding to U.S. Pat. No. 3,956,667. This device is utilized for picture reproduction on so-called flat screens as well as in gas discharge displays.
Display devices of this type function according to the principle of the spatial separation of electron generation and electron acceleration. As stated above, the device is divided into two chambers which are connected with one another via a conductor matrix formed on a perforated control disc by intersecting lines and columns of conductors. The chamber between the cathode or cathodes at the rear plate and the line conductors, which serve as auxiliary anodes, on the conductor matrix is the chamber wherein gas discharge takes place. The other chamber is the post-acceleration chamber which is between the column conductor side of the control disc and a flat annode which may be a luminescent screen electrode. By selectively driving one of the auxiliary anodes, a wedge-shaped gas discharge volume arises between the cathode and the auxiliary annode over the entire line length. By simultaneously driving one of the strip-shaped matrix column electrodes, plasma electrons which are generated in the gas discharge area are drawn through the perforation at the intersection point of the line and column conductors into the post-acceleration chamber and are accelerated to the anode. At the point of impact on the screen, a light point arises on a luminescent material layer which is deposited on the anode which corresponds to the image of the intersection point of the matrix which was selectively driven. The column and line conductors on the control disc are selectively driven according to a time-related course and intensity whereby symbols and pictures can be presented on the luminescent screen.
A further gas discharge display device having spacing elements is known from German OS No. 27 50 587 wherein ridges having a constant wall thickness are provided between the control disc and the post-acceleration anode, those ridges extending in the plane of the control disc past which the control disc perforations are guided and which run in segments alternatingly parallel and diagonally to the conductors which are facing the ridges.
For maintenance of spacing in a gas discharge display device between the control disc and the luminescent screen, it has been proposed in German patent application No. P28 55 108.8, corresponding to U.S. co-pending application Ser. No. 096,920 to arrange several perforated glass foils adjacent to each other which each have metallized surface layers. The metal layers carry floating potentials and thereby homogenize the acceleration field.
In each of the devices described above, it is a problem to make use of a high post-acceleration voltage in the post-acceleration chamber without bringing about arcing or flash over. Such arcing generally occurs between supports which may be present between the anode and the control disc in order to maintain a proper spacing therebetween, or may occur between the control disc and the material used to seal the post-acceleration chamber in a gas tight fashion.